Recording and reproducing sound



April '15, 1941. E. w. HULLEGARD 2,238,733 i RECORDING AND REPRODUCING SOUND 'F iled March 17,-1938 2 Sheef's-Sheet 1 a r g 1 5 r v v Ap 1941? a w. HULLEGARD 2,233,733

nsconnmsmn REPRODUCING scum:

Filed'March-l7. 1938 2 Sheets-Sheet 2 iinventov (Ittorneg Patented Apr. 15, 1941 UNITED STATES PATENT OFFICE 2,238,733 I imconnmc AND nnraonucmc SOUND an: winema- 'Hnllegird, Stockholm, Sweden,

assignor, by mesne assignments, to Radio Corporation 01' America, a corporation of Delaware Application March 17, 1938, Serial No. 196,554 In Sweden March 23, 1937 LCIa-ims.

illumination of the light-sensitive medium is quired on which. illumination the sound oscilla tions are optically superposed so that the background" will be much more silent than in previous systems having such a biasing illumination. In a known system the podtive and negative half-waves oi the sound curve are recorded each in one of two co-extensive tracks which necessiand I on the right hand side of the diaphragm. The fields 4 and 5 have one distinctive colour and fields 6 and I another distinctive colour. The triangular fields turn their points towards one another as shown while leaving an opaque zone between opposing points.

Further condensing lenses La and L4 and a slit device S: are positioned in a straight line between the oscillating mirror 2 and a light sensitive band 8 in such an angular relationship to the path between parts I and 2 that in an average position of the mirror 2 an image of the diaphragm S1 is projected on the slit device S2.

tates the provision of complicated apparatus,

having means for the simultaneous reproduction of two tracks. These two tracks require further a space of the light-sensitive medium, such as a film,,which is double that, Of an ordinary single-,

track.

According to the present invention said inconvenience is eliminated by arranging that the pomtive and negative half-waves oi the sound curve are not recorded in positions transversally displaced in relation to one another but in one and the same track while receiving such distinctive properties that the record of each half-wave eouldbeseparatelyreproduced. Incasethefilm is color-sensitive the positive and negative haliwaves of the sound curve could be converted each to a light bimdle of a distinctive color, to which the him is exposed.

The invention will now be more fully described with reference to the accompanying drawings illustrating by way oi example two embodiments of the invention. 0n the drawings, Fig. 1 is a perspective and diagrammatic view of a preterred embodiment of a recording device whereas Iflgz': is a circuit diagram 0! a reproduction device, Hg.3isasimilardiagramoiarecorderadapted toproduceavariahledensityrecordandl'lg. 1! illustrates a modified type of reproducer in which thetaophotoelectricelementsarearrangedwlth' asin'gleanodewithinthesamecontainer.

Inli'lg.1,condensinglenseshandhanda gdiaphragmsiarepositionedinastraightline The sharp-edged slit 9 provided therein has a width corresponding to the opaque zone between opposing points in the diaphragm S1 so that in the mentioned position of the mirror the image of the opaque zone covers the slit 9 and no light can penetrate to the colour-sensitive film 8.

The mirror 2 is connected to an oscillograph responsive to the sound to be recorded and which is not shown on the drawings.

when the mirror 2 starts oscillation the image of the diaphragm S1 oscillates to and from over the device So so that the translucent portions 4 and I alternating with the portions 5, 1 send light of corresponding colour hro'ugh the slit 9 on to The transve width or, in this instance, the vertical exte ion of the bundle of rays reaching the film will apparently depend on the vertical dimension of the translucent portions I to I projected on .to the slit device and thus on the angular deflection of the mirror 2 or the amplitude of the sound wave correspondin thereto. Provided the film band 8 is moving at a sufiicient rate. cross-wise to the slit 9 there will accordingly be recorded impressions which, when the film is developed, will appear as oblong traces II, II of the one or the other colour on an opaque background depending upon the translucent portions 4, 5 or i, I which is operative at the moment.

.In 1 .g. 2 is shown a reproduction device consisting of a light source l2, condensing lenses Ls and I4, stationary mirrors l3, it, put at an angle .to one another, colour filters S; and S4, each letting through only light corresponding to the one colour of the translucent portions 4, i or I, I respectively, and photo-cells P1 and Pa. These lattes are associated in push-pull-connection with an amplifier A and a loud-speaker B.

when the coloured film I is passed between the lenses Ls and Ls the'bundle of light will pass aiternatelytracesoitheoneortheothercolour or the passing film band land light of alternating colour will be reflected at the mirrors l3 and H on to the filters S: and S4 to actuate the one and the other of the photo-cells P1 and P: respectively, so that the amplifier A and loudspeaker B will respond.

In the shown embodiment there are two pairs of opposing translucent filter portions 4, 6, and 5,

I respectively. Instead thereof only one pair or several pairs of opposing translucent portions can be used. The points of such portions need not be positioned exactly opposite one another,

. reckoned in a plane parallel with the path of movement of the film band, but may be staggered in which case the tr aces on the film band will 'be correspondingly staggered although grouped symmetrically in regard to an imaginary base line on the film which line is parallel with the path of movement of the film.

The two photo-cells shown in Fig. 2 could be combined as shown in Fig. 4 to a single one having for instance two cathodes l1 and i8 and one anode It. In this arrangement, the lenses l5 and I6 perform the same function as the reflectors I3 and ll of Fig. 2.

Whereas the above described apparatus refers to such sound films which are modulated according to the amplitude method the invention could likewise be applied to sound films, based on an intensity-modulation, and in systems, using a combination of amplitudeand intensity-modulation.

Thus, if the aperture plate Sr be modified so that its center section 3 is opaque, its left hand section 4 passes only red light and its right hand section 6 passes only blue light, a variable density record is produced. This necessarily follows from the fact that when the mirror 2 is at rest no light is passed through the slit 5, and when the light beam is -vibrated transversely of the slit a red penumbra shadow is-produced for one direction of the vibration and a blue penumbra shadow is produced for the opposite direction of vibration.

In this record the alternate half cycles 20 and 2! are of different colors, as indicated in the drawings. This type of record may evidently be reproduced by any repmducer involving a colorselecting prism or other device suitable for causing light modulated by alternate half cycles to be applied respectively to the cathodes l1 and It. The reproducer of Fig. 4 is suitable for this purpose. This reproducer is also capable of reproducing either of the two tracks of the record of Fig. 1.

The foregoing method and apparatus are particularly useful with the present type of color films wherein a plurality of color-sensitive layers are provided and the exposure and development produce appropriate colors in each of these layers,

as distinguished from earlier types of color-films type including-a film having symmetrical images of opposite half cycles of sound waves thereon in different colors in axial alignment, and an opaque background surrounding said wave images.

4. A sound record of the photophonographic type including a film having symmetrical images i of opposite half cycles of sound waves thereon in axial alignment in different colors, and an opaque background surrounding said wave images.

ERIK WALDEMAR HULIEGARD. 

